Will there be some kind of mass-unit transport unit?

One-shot rockets == happy dance time. Much more interesting, better price-designed, and probably going to encourage better game strategy.

The word from the devs is that multi-unit transports are a lot of work to code and debug, and it's fairly tedious. So I would guess that if and when they're implemented it'll be post-release.

Transport structures like the unit cannon and teleporters seem like a better bet.

Where did they say that? I would actually like to read that thread.